1. Field of the Invention
The present invention relates to a method of prognosis, more particularly to a method of prognosis of a blood-related disease or hematological malignancy using a magnetic resonance imaging (MRI) scanner.
2. Description of the Related Art
Recently, it is well recognized that development and progression of cancer is related to angiogenesis. Hence, it is possible to predict progression of cancer (e.g., bone marrow-related malignancy, such as acute myeloid leukemia) by evaluating abnormality of angiogenesis.
Conventional follow-ups of patients under treatment for leukemia require the patients to undergo bone marrow biopsy on a regular basis so as to evaluate recovery of the patients. However, in the process of bone marrow biopsy, the patients have to endure pain, and hence bone marrow biopsy cannot be repeated within a short duration of time. Furthermore, data of angiogenesis obtained by bone marrow biopsy is static and is limited to the area of the bone marrow biopsy specimen, and thus cannot be used for observing real-time in vivo vascular perfusion and changes in permeability. Therefore, the monitoring of therapeutic outcome of leukemia is limited.
To address this issue, Shih T. T. et al. proposed in “Functional MR Imaging of Tumor Angiogenesis Predicts Outcome of Patients with Acute Myeloid Leukemia”, Leukemia 2006; 20(2):357-62, a method of prognosis of acute myeloid leukemia using a MRI scanner. This method performs a training procedure with a group of patients so as to determine a cutoff point for categorizing the patients into one of a high-risk group and a low-risk group. The cutoff point is further used for evaluation of angiogenesis and prognosis of leukemia. As shown in FIG. 1, the training procedure includes six consecutive steps.
In Step 1-1, a patient is injected with a contrast agent while the patient is scanned using a MRI scanner (the MRI scanning starts 10 seconds before the patient is injected with the contrast agent, and then the injection and the scanning continue concurrently), that is configured according to a configuration parameter set, so as to acquire a magnetic resonance (MR) image set of the patient.
In Step 1-2, for each image of the MR image set, a region of interest (ROI) is selected, and an intensity value of the ROI is obtained as a sum of pixel values of all pixels in the ROI. A time-signal intensity curve is subsequently plotted using the intensity values of the images in the MR image set.
In Step 1-3, a physical parameter is acquired from the time-signal intensity curve. The physical parameter can be a peak enhancement ratio or an initial maximum enhancement slope.
In Step 1-4, Step 1-1 to Step 1-3 are repeated with different patients to acquire different physical parameters. It is to be noted that the same contrast agent and MRI scanner configuration parameter set are used in this step.
In Step 1-5, the physical parameters of the different patients are analyzed using classification and regression tree (CART) techniques with reference to conditions of the patients so as to acquire a cutoff point of the physical parameter. The cutoff point categorizes the patients into one of a high-risk group and a low-risk group. The patients in the high risk-group have a higher angiogenesis rate and a poorer prognosis, which means the patients have a lower overall survival (OS) and a lower disease-free survival (DFS) compared to the patients in the low-risk group.
After completion of the above-mentioned training procedure, a prognosis of a patient with leukemia can be obtained by comparing the physical parameter of the patient (acquired through Step 1-1 to Step 1-3) with the cutoff point (acquired in Step 1-5). According to the physical parameter and the cutoff point, the patient is categorized into one of the high-risk group and the low-risk group, and evaluation of angiogenesis and prognosis of leukemia can be evaluated therefrom. It is to be noted that in the prognosis, it is mandatory to use the MRI scanner and the configuration parameter set used in the training process. Preferably, the same contrast agent is used in the prognosis.
The method proposed by Shih T. T. et al. uses dynamic contrast-enhancement magnetic resonance imaging (DCE-MRI), which is fast, non-invasive, permits repeated measurement within a short duration of time, and determines a specific cutoff point. Nevertheless, the cutoff point is suitable for use only if the MRI scanner and the configuration parameter set used for deriving the cutoff point are used. If other hospitals use another MRI scanner or configuration parameter set, the cutoff point cannot be used and the same process needs to be repeated for a certain amount of patients followed by subsequent analysis of the cutoff points. This is because the physical parameter obtained in the training procedure and the cutoff point derived therefrom are based on a particular model of the MRI scanner and a particular configuration parameter set. Therefore, if a different MRI scanner or a different configuration parameter set is used, it is necessary to perform the training procedure so as to determine a corresponding cutoff point. In addition, if a different contrast agent is used, the training procedure needs to be performed so as to acquire a corresponding cutoff point.